Hey, Matt Colan!

[Ted Fancher]

Hey, Matt.  Have you got your toy back in the air yet?  Seems like I've been watching a slow motion train wreck following all of your misadventures.  Hope luck has turned around for you.

Ted

[Matt Colan]

Hi Ted,

I flew it twice since the repair. The plane flies fine, it needs a touch more nose weight because the rudder is heavier than the 1st one. The problem is that the motor run isn't worth anything anymore. We think I bent the connecting rod on the impact. Im going to need a new connecting rod and gasket set.

My primary airplane for the team trials now is my grandfathers P-40, which we spent some time with getting it in better trim. Now it flies very well!  Derek Barry is bringing his dreadnought from a couple years ago for me to try out when I'm there. If I like it better, I'll fly his plane rather than the P-40.

BTW, I fly my patterns different than my grandfather (he flies big and soft) and with me flying harder corners, I uncovered an issue with his P-40 on 120 degree turns. It stalls. The plane is not overweight (65 ounces and 705 sq inches of wing area). Besides softening up the corners, what's a possible cure to that issue?

[PJ Rowland]

I have a sure fire cure for a model that stalls during the corners... however its not widely accepted ...

Dereks Dreddy should be amazing for you.

[Randy Powell]

What, PJ. Deceleration trauma?

Matt,

For stall in corners, there are a couple possible solutions. Bigger flaps or more flap movement is the easiest. Sometime more horse power can drag the plane through corners more crisply, but that mostly hides the problem. Or you can fly faster generating more lift and so curing the stall.

[Howard Rush]

Or you can fly faster generating more lift and so curing the stall.

Or you could pay attention in physics class.  Lift is indeed proportional to airspeed squared, but the amount of lift you need to go around a corner of a given radius is also proportional to speed squared. 

[Tim Wescott]

Or you could pay attention in physics class.  Lift is indeed proportional to airspeed squared, but the amount of lift you need to go around a corner of a given radius is also proportional to speed squared.  

But the ability to see a square corner is inversely proportional to speed to some positive power, so that's all right.

edit

Actually, the Reynolds number would go up so there may be some slight increase in the available lift coefficient.  Prolly not enough to make nearly as much difference as the perceptual one, but still a real physical one, none the less.

[Matt Colan]

Or you could pay attention in physics class.  Lift is indeed proportional to airspeed squared, but the amount of lift you need to go around a corner of a given radius is also proportional to speed squared. 

Physics starts in two days for me 

[PJ Rowland]

Taken directly from Wikipedia :

Vortex generators delay flow separation and aerodynamic stalling, thereby improving the effectiveness of wings and control surfaces.

( I will add )

A Micro Vortex Generator

Creates a tiny vortex in the airstream over an airfoil. This vortex energizes the normally stagnant boundary layer of air on the wing's surface. An energized boundary layer is more resistant to flow separation than a stagnant boundary layer. The result is that airflow "sticks" to the wing better, permitting flight at lower airspeeds with improved control authority.

[Howard Rush]

They're used for fixing specific aero problems.  They are more applicable to F2B than to AMA airplanes, because they make the surfaces on which they are affixed hard to wax.

[PerttiMe]

A Micro Vortex Generator

How small is a micro vortex generator?
A piece of sewing thread? Thickness of a layer of paint? A surface that is not polished?

I hear F3A R/C aerobatics guys saying that their ships don't fly right if they polish the wings.

[Brett Buck]

BTW, I fly my patterns different than my grandfather (he flies big and soft) and with me flying harder corners, I uncovered an issue with his P-40 on 120 degree turns. It stalls. The plane is not overweight (65 ounces and 705 sq inches of wing area). Besides softening up the corners, what's a possible cure to that issue?

    Tape some .015 or .018 flying lines along, or just in front of, the high point of the airfoil, top and bottom.

     I am a little surprised that it is stalling at that wing loading. What engine does this airplane have?

     Brett

[Matt Colan]

    Tape some .015 or .018 flying lines along, or just in front of, the high point of the airfoil, top and bottom.

     I am a little surprised that it is stalling at that wing loading. What engine does this airplane have?

     Brett

I was surprised that it's stalling also. It's a ST 60 powering it. The airfoil is the SV-11 wing, but he put bigger flaps on compared to the regular SV wing planform (3 inches at the root, 2 inches at the tip).

Here's a picture of it, you may have seen it at the NATS.

[Ron Merrill]

Matt, not to get off subject, but did Irene treat you ok? I know you have a lot of flooding going on up there. Ron.

[Matt Colan]

Matt, not to get off subject, but did Irene treat you ok? I know you have a lot of flooding going on up there. Ron.

Hi Ron,

We got pretty lucky compared to the southern part of the state.  If anybody's been keeping up with the news, southern Vermont saw catastrophic flooding!  By me, my version of catastrophic flooding was my backyard/flying field flooding.

Lake Champlain went up 2 feet, a tree went down next door to me, the corn in our garden might be ruined as it got blown all over the place, and we lost power around 12:30 early monday morning.  It came back somewhere around 2 in the morning.

[Randy Powell]

Howard,

I was talking about practical application and experience. From my experience, if you make the flaps bigger or increase the amount of deflection, you get more lift (not to say there are not drawback to this including by not limited to increased drag). You can also increase air speed which will increase lift available, though again, there are drawback including that my reflexes often can't keep up with the plane if it's going much faster than 4.8 second laps. And as you point out, it's not proportional and other problems are created. And this is only useful if it just stalls very slightly. If the thing drops like a rock, then it's not much help. There are obviously a ton of other factors, but I was just speaking to Matt's question: what he could do to try to help the problem. I didn't think he was looking for an in depth discussion of the physics principals involved, just what he could possibly do about the problem.

I liked Brett's suggestion as a way to remediate flow separation. That could help, too.

[PJ Rowland]

I make mine out of carbon Fiber. You can still wax it.. I have refined it over the last 13 yrs now, to only have 1 pair about 6" in from the Fuse, just at the highpoint.. I found no extra effectiveness running more than that.. 1 Pair top / bottom. Height - I agree its difficult to make it as small as it would actually need to be, however this doesnt seem to hamper performance. Mine are 5mm long x 3 mm high.


I dont think its applicable to every model.. If its light, its not really required - it doesnt "aid" performance if the model is within a certain design envelope.. I like to use it these days to help increase drag and load up the engine.


I dont' disagree with brett's reccommendation, its a more crude way of doing similar.. A VG will create an energized boundary layer, whereas taping wire will disrupt the airflow. They use VG technology on alot more things than one might suspect, from F1 Racing to the latest BMW M3.. Even golf ball designs are based on a similar theory.

[louie klein]

Hi Matt! A belated congrats for the great job you and gramps did at the NATS. That was one giant step for the first time in that competition! Wow do I envy you guys.---LOUIE 

[Brett Buck]

I was surprised that it's stalling also. It's a ST 60 powering it. The airfoil is the SV-11 wing, but he put bigger flaps on compared to the regular SV wing planform (3 inches at the root, 2 inches at the tip).

Here's a picture of it, you may have seen it at the NATS.

     That does surprise me, although it would less likely to stall if you put in a PA40/51/61/65 running 4" of pitch. Try the turbulator trick, that's usually our last resort solution.

    I presume that you have already sealed the flap and elevator hinge lines.

    Brett

[Matt Colan]

     That does surprise me, although it would less likely to stall if you put in a PA40/51/61/65 running 4" of pitch. Try the turbulator trick, that's usually our last resort solution.

    I presume that you have already sealed the flap and elevator hinge lines.

    Brett

Yep, hinge lines are sealed.

All the extra rear exhaust engines we have (2 PA 40s, and 2 OPS 40s) I think are too small putting in a plane this size.

[Howard Rush]

I didn't think he was looking for an in depth discussion of the physics principals involved, just what he could possibly do about the problem.

I liked Brett's suggestion as a way to remediate flow separation. That could help, too.

That's not in depth; it's the most basic principle in the effect of speed on turning a corner.  If going faster helps your plane, I'd guess it's because of something springy in your control system. 

Brett's trick is easy to try, but I wouldn't count on it working every time.  If the flow needs tripping to go from laminar to turbulent, the wire might trip it.  It could also cause separation, which is why foam combat planes with dents where the spars run suck (not in the aerodynamic sense). 

Here's a trip strip we put on the stabilizer of a plane Windy was flying at a contest down south.  I had one on the bottom of the stab on my recent Impact to help with the transition from outsides to insides in the horizontal eight.  I don't know if either one did anything.  Probably a little better way to do it is a spanwise row of semicircles (semicylinders, I guess) about .004" high.

[Randy Powell]

Howard,

You do a lot of stuff that is extremely cool. Probably doesn't do all that much, but it is cool.

[Brett Buck]

Brett's trick is easy to try, but I wouldn't count on it working every time.  If the flow needs tripping to go from laminar to turbulent, the wire might trip it.  It could also cause separation, which is why foam combat planes with dents where the spars run suck (not in the aerodynamic sense). 

     So far, it's worked to some extent every time we have tried it. It even helped Uncle Jimby's appalling "Frankenstunt", but not enough.

    Brett

[Howard Rush]

You do a lot of stuff that is extremely cool. Probably doesn't do all that much, but it is cool.

You are way ahead of me in the cool dept.  Now get that low rider working.  Use trip strips on the wheel pants if you have to.

[PJ Rowland]

Installing 1 pair of VG's top and bottom Inboard and outboard is so easy - its more effective, it works - there is no guess work involved. Run them 30 degree's to the airflow, in a Pidgoen toe configuration or.. you can also run them inboards facing 1 direction and outboard facing the opposite direction at the highpoint. Infact I've played around with them in various locations and its just as effective 1" forward or back of that location.

I agree with Howard - buffing a model with them is annoying you need to be careful.

I found more than 1 pair isnt anymore effective, on the stab isnt effective at all ( or that I could detect ) I have flow back to back flights with them on and off with measurable tangable results.


Try this experiement, take a glass of water and adgitate the water with your hand and time how long it takes for the water to settle. Now circle your finger around like a little whirpool and measure how long it takes to settle back down.. You will find its substantially longer.

Adgitated water takes between 6 - 10 seconds to settle
Circled whirpool water takes 15 - 23 seconds to settle.


You are giving the boundary layer alot more energy to work with compared to normal turbulent airflow of a piece of wire. VG's force the airflow to move down the wing in a spiral fashion, becasue of the inheriant nature of a Vortex form, it lasts longer, moves further down the wing and allows for less flow seperation than almost any other single form of boundary layer seperation.

I will admit, I dont work in the aerospace industry - however I have been experimenting with VG's of this style and reading as much as I can on the subject since 1996. Thats 15 years of development, I think it counts for something when you consider how many seperate aircraft I've flown them on in countless configurations.

Again I say its not for everyone, If you have a light plane I dont think it will help with stall speed. However most of my currect crop of planes are considered " comp spec weights " I still find I prefer the feel of being able to easily load the engine and to a certian degree control wingtip rocking due to turbulance in windy conditions also control aircraft speed - eg windup. Obviously a good pipe engine or electric doesnt effect this part.
 
I simply offer this up as part of the ongoing want for information for the Stunt community.

Like Howard with his "rush boost tabs" These technologies are avaiable for those who wish to go down another route.

[M Spencer]

A Gloster Javlin is a lot of vortex generators , with an aeroplane under them somewhere . 

[roger gebhart]

Many of the ag airplanes have vg's now including mine. Seems like the airplane gets off the ground a bit quicker and feels better at slower speeds in the turn. they run full span about 10 inch apart. Don't need them on bottom for my purpose. FWIW

[Doug Moon]

I quick search for Vortex Generators for the Gloster Javelin pulled up this pic.

Plus the page with this pic is pretty informative from a general standpoint about how they work.
 
http://www.google.com/imgres?imgurl=http://www.aerospaceweb.org/aircraft/fighter/javelin/javelin_18.jpg&imgrefurl=http://www.aerospaceweb.org/question/aerodynamics/q0009.shtml&usg=__vmEcw6_0I4YuruFPyYGhurgVxc0=&h=261&w=550&sz=19&hl=en&start=1&zoom=1&tbnid=insVapVMGocR2M:&tbnh=63&tbnw=133&ei=2zBeTuu-Joba0QHMt4TwDw&prev=/search%3Fq%3Dgloster%2Bjavelin%2Bvortex%26hl%3Den%26gbv%3D2%26tbm%3Disch&itbs=1

You can see they are utilizing them at the fore and aft locations.  This makes sense as you want the air sticking to the flying surfaces for sure.

Plus you notice they are actually little wing like structures that jut upwards off of the wing. I noticed them on PJ's Dad's plane at the nats.  Two small pieces of carbon fiber blade spar sticking up out of the wing about 1/8" or less set at a pigeon toe angle to each other.  Just as he said about 6" out from the fuse.  They were not utilized across the whole wing.  I find this interesting.  I would imagine they are most effective right there as this is the area where the plane that is transitioning from prop wash to regular airspeed??

I remember reading about them many years ago and thinking they would be great additions to a stunt plane.  Especially if you want to fly slow as they really help out at low speed maneuvering.  Or what is considered low speed maneuvering for a particular wing.  I have never tried them as of yet but I am thinking I might on my current damaged yet still very good flying model and see if I can get any extra performance from her.

The odd thing about Matt’s plane stalling is the wing loading is in the proper range.  I am wondering if there is a control issue.  I had this very thing happen to me several planes ago.  I built the model 675 sqrs 60 oz.  It was stalling horribly in last corner of the triangle and hourglass.  It was a tad tail heavy but that wasn’t the issue.  It was flat out giving up in those two corners.  In most other areas of the pattern it was very flyable.  It had removable flaps so we tried bigger flaps.  No change.  We tried MAAAAAAAAAASIVE amounts of nose weight to cure the tail heavy feel as well.  No change.  Tried flying it faster and faster as well.  No good.  It just didn’t make sense why it would stall at that wing loading.  Finally one day we stuck a protractor on the side of the plane and measured the deflections.  DING DING DING!!  Turns out I had made the mistake of flipping the pushrod connections at the flap horn.  The elevator was deflecting way way way more than the flap and it was cause of the stall.

We quickly put the plane under and performed surgery.  We went in through her under belly to get to the heart.  An hour later and she was recovering nicely with no noticeable scars.  After a nights rest the next day she was able to perform as expected and became a good flying plane in my stable for quite a while.  I was able to take out all the nose weight and retrim it into a very good flying plane.  She remained one of my trusted warriors until she was traded to the northeast.  They treated her well and flew her all the time.  I saw a pic of her taking off at one of the Brodak Flyins in Flying Models.  I think she still flys some patterns from time to time somewhere.
 
Check those controls.  Even just a few more degrees elevator than is needed can really cause some issues.

[Derek Barry]

Maybe, just maybe, you are hitting the corner too hard. As Billy use to tell me "Fly the corner! Even hard corners have to be flown".  I think some of these guys overcomplicate problems. Speed the plane up a little and fly a little softer. I watched you at the nats, if there is one thing you do have, it's corner.

Derek

[PJ Rowland]

Doug - Even my Gieseke Nobler at the US Nats had them.. I managed to hide them really well - unless you were looking for it.. you may not have noticed.

I did try them near the flap also - I found no additional improvement. For me, thats what It has ALWAYS been about, improvement. I cannot tell you how many flights I've had where I experimented. Using the carbon fiber and some tweezers, and zap, takes all of 2 minutes to adjust them. - Obviously I wouldnt do it with a nice painted model. however once a model reaches a certain " age " you stop thinking about its looks..

I tried literally hundreds .. ( well maybe not 100's . but an alot. ) of seperate configurations. Initally they were all along the wing, just as you see it in your diagram. Over time - some broke off.. and performance didnt seem to be effected. So I would start to expeirment with different configurations. The first sets were rather crude by what I do today - 1/ 64 ply, in a triangle shape. I even went as large as 1/2 " long !

I tried them infront of the flaps, on the fuse, on the tail, on the Stab, on the rudder.. I tried the Bear Plates, on and off.. had VGS on and around them.. Each time making notes on performance - compared to the baseline.

Over time.. I found I could run fewer and fewer.. in 2004 I was down to 1 set at the root and 1 set at the tips.. always thinking that I needed them at the tips.. Whenever I removed it.. It was in the back of my mind - Im sure there was a difference.. however it was not something I could quantify. Even the Bomber had 2 sets ..

As mentioned the 2 at the tips - I never totally convinced myself that they were working.. or not working.. there was such a small difference I just ran them for maybe 4 years in that configuration. Eventually I settled on 1 pair near the Root.. but.. 6" inward. I found too close to the wing I get less effectivness..I can only reason that this is due to the fact there is not enough of the wing being energized.
Perhaps this explanation is why I found such a little alteration in the early days from running 2 sets.. the first set was always alot closer to the Root, compared to todays versions.  

I suspect you could put them in the middle of the wing and get similar performance.. I chose to put it there, Mainly to help reduce the prop wash into the Stab. How good does it work ? I have no idea.. I would have to move them to more in the middle.. perhaps I will experiement with that later - however for now its working perfectly.

For me..... the Idea of adding 1 pair of VG's is done before the model is even test flown - I put it in the same catagory as sealing hinglines.. a performance improvement device or PID.


Incidently, I find it impossible.. to stall no matter now hard I bang the corner.. Not like what Matts talking about. Im not just talking about my Nobler, remember I do fly normal comp spec planes usually..

I have also never experienced "dead" spots of air.. like what happened to your model Doug ( I'm not having any sort of go at you mate.. that was 1 in 1000.. please..very unfortunatly and sorry to see..  ) I postulate that the even if the model does hit a "dead patch" there is still plenty of residual Vortex airflow to keep the model in the air.. Think of it.. like a bird facing into the wind.. they are stopped, but are not dropping becasue of the airflow moving over the wings its equal to normal lift at forward speed.
I suspect I get a similar thing happening with the addition of VG's - The spinning Vortex by nature would take longer to exit the wing compared to normal flight.

I also notice flying in strong winds, I dont get knocked around as much, and almost NEVER have the model suddenly drop out of the sky downwind in a landing. On that note.. landing with VG's is difficult, you need to really LAND it.. whereas a model without, you can let it drop naturally.


I guess the bottom line of all this is simple - Like anything in our sport try it for yourself, and make your own assessments.  I can supply any drawings or photo's of how I set my system up. The carbon I use is from APC its .04 or .03 thickness Carbon laminate. Cut, sanded and glued on.


Doug Id be very interested to hear your feedback if you wanted to try them. It wont radically alter your engine setup .. might just load it up a little more.. more pitch or more revs..  Let me know if you need some more info.

You can see them on my Nats Gieseke Nobler.. from this angle.

[Randy Powell]

Howard,

Yea, but I don't have flap tab thingys or spiffy flow redirection gizmos.

[Doug Moon]

PJ, where do I start? 

How far out to I place the first one?

Then how far apart are they? 

Do they have shape or are they just square?

Thanks

[PJ Rowland]

I will post some information in a new thread - with photos - Wont Hijack the thread anymore.

Tomorrow..

[PJ Rowland]

Randy.. your not willing to step out beyond convention thats why you dont have anything like that on your ships..

Plain .. plain.. plain..  Set in your ways of playing it safe..

Mr Conservative..

[Steve Fitton]

Matt, are you sure it isn't just hinging in the corner? That would make much more sense than a stall at the given weight.

Also, bending a rod in the accident the ROJett 76 was in seems a bit improbable.  I suspect a leak or other problem in the fuel or exhaust system from the cash or the repair process as much more likely.

[Howard Rush]

Matt, are you sure it isn't just hinging in the corner? That would make much more sense than a stall at the given weight.

Also, bending a rod in the accident the ROJett 76 was in seems a bit improbable.  I suspect a leak or other problem in the fuel or exhaust system from the cash or the repair process as much more likely.

Good points.  I was thinking that about the rod, too.  What are the symptoms?

[Matt Colan]

Matt, are you sure it isn't just hinging in the corner? That would make much more sense than a stall at the given weight.

Also, bending a rod in the accident the ROJett 76 was in seems a bit improbable.  I suspect a leak or other problem in the fuel or exhaust system from the cash or the repair process as much more likely.

I might have thought it was a fuel system issue, except the motor doesn't feel right when I turn the prop over, it doesn't sound right, and the needle is a full turn out from where it was before the crash to get the right RPM.

The header was loose when we inspected it after I flew it to see what might be the issue.  We tightened the bolts and mounting bolts just to see if that made a difference, and other than running a little quieter, made no difference in the feel, and sound of the engine.

[Matt Colan]

I quick search for Vortex Generators for the Gloster Javelin pulled up this pic.

Plus the page with this pic is pretty informative from a general standpoint about how they work.
 
http://www.google.com/imgres?imgurl=http://www.aerospaceweb.org/aircraft/fighter/javelin/javelin_18.jpg&imgrefurl=http://www.aerospaceweb.org/question/aerodynamics/q0009.shtml&usg=__vmEcw6_0I4YuruFPyYGhurgVxc0=&h=261&w=550&sz=19&hl=en&start=1&zoom=1&tbnid=insVapVMGocR2M:&tbnh=63&tbnw=133&ei=2zBeTuu-Joba0QHMt4TwDw&prev=/search%3Fq%3Dgloster%2Bjavelin%2Bvortex%26hl%3Den%26gbv%3D2%26tbm%3Disch&itbs=1

You can see they are utilizing them at the fore and aft locations.  This makes sense as you want the air sticking to the flying surfaces for sure.

Plus you notice they are actually little wing like structures that jut upwards off of the wing. I noticed them on PJ's Dad's plane at the nats.  Two small pieces of carbon fiber blade spar sticking up out of the wing about 1/8" or less set at a pigeon toe angle to each other.  Just as he said about 6" out from the fuse.  They were not utilized across the whole wing.  I find this interesting.  I would imagine they are most effective right there as this is the area where the plane that is transitioning from prop wash to regular airspeed??

I remember reading about them many years ago and thinking they would be great additions to a stunt plane.  Especially if you want to fly slow as they really help out at low speed maneuvering.  Or what is considered low speed maneuvering for a particular wing.  I have never tried them as of yet but I am thinking I might on my current damaged yet still very good flying model and see if I can get any extra performance from her.

The odd thing about Matt’s plane stalling is the wing loading is in the proper range.  I am wondering if there is a control issue.  I had this very thing happen to me several planes ago.  I built the model 675 sqrs 60 oz.  It was stalling horribly in last corner of the triangle and hourglass.  It was a tad tail heavy but that wasn’t the issue.  It was flat out giving up in those two corners.  In most other areas of the pattern it was very flyable.  It had removable flaps so we tried bigger flaps.  No change.  We tried MAAAAAAAAAASIVE amounts of nose weight to cure the tail heavy feel as well.  No change.  Tried flying it faster and faster as well.  No good.  It just didn’t make sense why it would stall at that wing loading.  Finally one day we stuck a protractor on the side of the plane and measured the deflections.  DING DING DING!!  Turns out I had made the mistake of flipping the pushrod connections at the flap horn.  The elevator was deflecting way way way more than the flap and it was cause of the stall.

We quickly put the plane under and performed surgery.  We went in through her under belly to get to the heart.  An hour later and she was recovering nicely with no noticeable scars.  After a nights rest the next day she was able to perform as expected and became a good flying plane in my stable for quite a while.  I was able to take out all the nose weight and retrim it into a very good flying plane.  She remained one of my trusted warriors until she was traded to the northeast.  They treated her well and flew her all the time.  I saw a pic of her taking off at one of the Brodak Flyins in Flying Models.  I think she still flys some patterns from time to time somewhere.
 
Check those controls.  Even just a few more degrees elevator than is needed can really cause some issues.

The controls are set at 1:1

[Matt Colan]

Maybe, just maybe, you are hitting the corner too hard. As Billy use to tell me "Fly the corner! Even hard corners have to be flown".  I think some of these guys overcomplicate problems. Speed the plane up a little and fly a little softer. I watched you at the nats, if there is one thing you do have, it's corner.

Derek

Hi Derek,

The night before the flyoff, I was flying with Richard Oliver, and got some coaching from him, Frank McMillian, and Les Demmet.  After we quit for the night, I backed off on how hard I was flying the corners. On video, they still looked razor sharp but the whole pattern was a lot smoother compared to top 20 day, where I occasionally overcontrolled it, and popped up slightly.

When I first saw felt and saw the plane stalling on the triangle, I thought I hit my own air since the plane shook as well as sink.  I backed up a good amount where there was no way I could hit my own air again, and the plane did the same thing.  On the hourglass, all it did was sink, it didn't shake.

I think those Vortex Generators may help it out.

[M Spencer]

Or ' blown ' flaps . !

[Steve Fitton]

Do you have room in the trailer to get the Trivial Pursuit to Muncie next week?  Even if end up not entering with it, there is such a brain trust there they can probably sort out all the problems, or at least tell you what is not wrong with it.

[Ron Merrill]

Matt, listen to Steve, and bring TP to trials if you can and let these people look at it, where else could you get so many good fliers and builders together to take a look at  your TP. IMHO.  Ron.

[Matt Colan]

Do you have room in the trailer to get the Trivial Pursuit to Muncie next week?  Even if end up not entering with it, there is such a brain trust there they can probably sort out all the problems, or at least tell you what is not wrong with it.

Hi Steve,

We're not bringing the trailer, otherwise I would bring the TP.  The way we pack for contests, we're only going to have room for one airplane.  There's nothing wrong with the plane, just the engine.  I do want to take it out and bring it so I could have RO have a look at it and see what he thinks is wrong with it.

[Randy Powell]

Matt,

That's a good idea. You can also just put it in a box and drop it to Dub Jett. He will tell you what's up.

[Ted Fancher]

Holy Cow!  I drop a little note two days ago and come back to find a novel!  Lots of interesting thoughts here.

I'd add two items I didn't see addressed in a quick run through.

First.  How sharp is the leading edge of the wing?  Brett and I could stall the first Great American ARF-OFF winner at will with the leading edge the way it came out of the carton (I forget the name of the ship.  One of Windy's that John ARFed with a big wing and huge flaps.)  A STREGA!  That's it. (They say the memory is the first thing to go...I don't remember who "they" were)

At any rate.  We took it to our flying field a week or so later along with some rasps, sandpaper and sticky monokote.  We rounded the leading edge as much as we could with the 1/4" square leading edge under the sheeting.  After that it was impossible to stall.

Second, I can't tell much about the flap configuration on the P-40 from the picture.  How large are they and are they full span or shorter?
The original TP, for instance uses less than full span flaps (which I prefer because the hinge loads are lower and the input forces less) which provide a poppier corner.  However, because it is severely weight challenged it had a tendency to stall in hot muggy weather.  I very slight increase in flap deflection for a given amount of elevator input was the final fix and it doesn't stall anymore.

The TP was also the first ship we tried the control wire turbulators on at a very muggy and drizzly team trials where it was stalling in the last corners of triangles and hourglasses.  The wires got us through the team trials just fine but the increased flap movement was a neater, and thus far equally effective, fix.  Hasn't stalled in many a year.  Worth noting that it currently weighs 72 oz and has a wing area of ~650-60 square inches.  It has also won a Team Trials, four Nats second places and two third places.  Pretty good record for a ship that's "too heavy" to fly well.

At any rate, let us know how long the span of the flaps is relative to the wingspan and the chord of the flaps at the root and tip so we can do a little grade school math (I leave all the complicated stuff to Howard and Brett who speak "numbers" fluently).

Ted

[Ted Fancher]

Hmmm, just looked at the picture and it looks like the flaps extend all the way to the tip and you said they were three inches at the root and two at the tip.  Couldn't get much bigger than that and you also said they're one to one ratio. 

Give us the word on the leading edge, and then...

Where is the CG located at the average chord.  If an airplane is real nose heavy it can still fly well if the controls can drive it to the required angle of attack but the forward CG also causes the lift required for a given rate of turn to increase because of the extra down load on the tail which increases the "weight" that must be carried by the wing in maneuvers and also demands more control deflection.  (Remember, if you move the CG forward enough you can get to the point that you need full up elevator to simply keep the nose level!)

Couple of things.  If the ship needs lots of deflection the flaps will increase the camber of the airfoil and, thus,  the angle of attack commensurately.  The resulting lift is necessary and, thus, desirable but the large deflection angle could also drive the wing closer to its critical angle of attack (the point at which the wing stalls no matter the speed at which the airplane is flying...what we call an accelerated stall in the biz).  This is, again, the primary reason I advocate aft CGs.  Takes less control deflection, requires less lift in maneuvers and has less tendency to open up in the wind.  Of course, how far aft you can go and maintain positive control-ability is limited by the tail volume and static margin (big tails).

At any rate...where's the CG and how big is the tail?

Ted

[Matt Colan]

Hi Ted,

The tail is 22% of the wing area. Not the biggest tail size in the world, but better than some. I don't remember the exact place where the cg is but it's just aft of the high point of the wing.

The flaps are full span, and the leading edge is definitely not sharp! I don't know how round it is if you want a precise measurement, but it's got an average round leading edge (it's an SV-11 wing with his own flaps and round wing tips)

[Ted Fancher]

OK Kid,  I'm running out of ideas.  Let me know more about the CG whenyou get a chance.  There's no obvious reason the airplane should be stalling.  hmmmmm

TEd

[Matt Colan]

OK Kid,  I'm running out of ideas.  Let me know more about the CG whenyou get a chance.  There's no obvious reason the airplane should be stalling.  hmmmmm

TEd

Hi Ted

When I fly it again, I'll let you everybody know what happens. It may or may not be a couple days before I fly again because the weekend looks like a washout.

[Doug Moon]

This might be a dumb question but on the TP is spinner backplate rubbing the plane?  And have you run the motor on the test stand since these issues started.  That would really tell you alot.  Is it the motor or the plane causing this?

Just a thought.

[Brett Buck]

This might be a dumb question but on the TP is spinner backplate rubbing the plane?  And have you run the motor on the test stand since these issues started.  That would really tell you alot.  Is it the motor or the plane causing this?

   I would also note that he extensively rebuilt the wing/fuse joint, and if that wasn't done quite right, vibration could be causing poor runs. Although the chances are any repairs made it stiffer, not flimsier.

    Brett